Dialer Interface - Teldat -3Ge-USB User Manual

Teldat S.A.
dialer user movistar
dialer-group 1
dialer bundle 1
#
interface Ethernet0/0
port link-mode route
ip address 172.24.80.15 255.255.0.0
#
interface Serial0/0
link-protocol sdlc
#
interface NULL0
#
interface Vlan-interface1
pppoe-client dial-bundle-number 1
ip address 1.1.1.1 255.255.255.0
#
interface Ethernet0/1
port link-mode bridge
#
interface Ethernet0/2
port link-mode bridge
#
interface Ethernet0/3
port link-mode bridge
#
interface Ethernet0/4
port link-mode bridge
#
ip route-static 0.0.0.0 0.0.0.0 Dialer1
#
dhcp enable
#
dialer-rule 1 ip permit
#
user-interface aux 0
user-interface vty 0
user privilege level 2
set authentication password simple threecom
user-interface vty 1 4
#
return

3.3.1 Dialer Interface

Configuring the 3Com router for WWAN connectivity through the Teldat-3Ge-USB with PPPoE is based on the cre-
ation of a dialer interface. The router establishes a PPPoE session through said interface and uses it to negotiate
and establish a PPP link with the WWAN mobile network. In the PPPoE session, the router acts as client and the
Teldat-3Ge-USB as server.
The dialer interface configuration shows the configuration for the PPP parameters (user and password) and the
definition for the MTU (maximum is 1492 bytes for PPPoE. There are also commands to configure port NAT and the
definition for the bundle and the group for the dialer interface.
When using PPPoE, it's very important to configure the maximum size of the TCP segment (MSS) to avoid problems.
Set the maximum size of the TCP segment to 1452 bytes to include the 20 bytes for the IP header and the 20 bytes
for the TCP header (MTU –20 –20 = 1452). If you don't configure this parameter, a host (e.g. a PC with an MTU of
1500 bytes by default) could negotiate a 1500 byte MSS. This results in packets received in the Teldat-3Ge-USB
(through the 3G modem), which are bigger than 1492 bytes. Said packets are consequently dropped as they cannot
be encapsulated in PPPoE to the router.
interface Dialer1
mtu 1492
nat outbound
link-protocol ppp
ppp chap user movistar
Teldat-3Ge-USB User Manual
3 Configuring in Generic mode
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